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Js how to set an item at a nested index in an empty array [duplicate]

I hope someone can help me with this Javascript.
I have an Object called "Settings" and I would like to write a function that adds new settings to that object.
The new setting's name and value are provided as strings. The string giving the setting's name is then split by the underscores into an array. The new setting should get added to the existing "Settings" object by creating new nested objects with the names given by each part of the array, except the last part which should be a string giving the setting's value. I should then be able to refer to the setting and e.g. alert its value. I can do this in a static way like this...
var Settings = {};
var newSettingName = "Modules_Video_Plugin";
var newSettingValue = "JWPlayer";
var newSettingNameArray = newSettingName.split("_");
Settings[newSettingNameArray[0]] = {};
Settings[newSettingNameArray[0]][newSettingNameArray[1]] = {};
Settings[newSettingNameArray[0]][newSettingNameArray[1]][newSettingNameArray[2]] = newSettingValue;
alert(Settings.Modules.Mediaplayers.Video.Plugin);
... the part that creates the nested objects is doing this ...
Settings["Modules"] = {};
Settings["Modules"]["Video"] = {};
Settings["Modules"]["Video"]["Plugin"] = "JWPlayer";
However, as the number of parts that make up the setting name can vary, e.g. a newSettingName could be "Modules_Floorplan_Image_Src", I'd like to do this dynamically using a function such as...
createSetting (newSettingNameArray, newSettingValue);
function createSetting(setting, value) {
// code to create new setting goes here
}
Can anyone help me work out how to do this dynamically?
I presume there has to be a for...loop in there to itterate through the array, but I haven't been able to work out a way to create the nested objects.
If you've got this far thanks very much for taking the time to read even if you can't help.

Put in a function, short and fast (no recursion).
var createNestedObject = function( base, names ) {
for( var i = 0; i < names.length; i++ ) {
base = base[ names[i] ] = base[ names[i] ] || {};
}
};
// Usage:
createNestedObject( window, ["shapes", "triangle", "points"] );
// Now window.shapes.triangle.points is an empty object, ready to be used.
It skips already existing parts of the hierarchy. Useful if you are not sure whether the hierarchy was already created.
Or:
A fancier version where you can directly assign the value to the last object in the hierarchy, and you can chain function calls because it returns the last object.
// Function: createNestedObject( base, names[, value] )
// base: the object on which to create the hierarchy
// names: an array of strings contaning the names of the objects
// value (optional): if given, will be the last object in the hierarchy
// Returns: the last object in the hierarchy
var createNestedObject = function( base, names, value ) {
// If a value is given, remove the last name and keep it for later:
var lastName = arguments.length === 3 ? names.pop() : false;
// Walk the hierarchy, creating new objects where needed.
// If the lastName was removed, then the last object is not set yet:
for( var i = 0; i < names.length; i++ ) {
base = base[ names[i] ] = base[ names[i] ] || {};
}
// If a value was given, set it to the last name:
if( lastName ) base = base[ lastName ] = value;
// Return the last object in the hierarchy:
return base;
};
// Usages:
createNestedObject( window, ["shapes", "circle"] );
// Now window.shapes.circle is an empty object, ready to be used.
var obj = {}; // Works with any object other that window too
createNestedObject( obj, ["shapes", "rectangle", "width"], 300 );
// Now we have: obj.shapes.rectangle.width === 300
createNestedObject( obj, "shapes.rectangle.height".split('.'), 400 );
// Now we have: obj.shapes.rectangle.height === 400
Note: if your hierarchy needs to be built from values other that standard objects (ie. not {}), see also TimDog's answer below.
Edit: uses regular loops instead of for...in loops. It's safer in cases where a library modifies the Array prototype.

function assign(obj, keyPath, value) {
lastKeyIndex = keyPath.length-1;
for (var i = 0; i < lastKeyIndex; ++ i) {
key = keyPath[i];
if (!(key in obj)){
obj[key] = {}
}
obj = obj[key];
}
obj[keyPath[lastKeyIndex]] = value;
}
Usage:
var settings = {};
assign(settings, ['Modules', 'Video', 'Plugin'], 'JWPlayer');

My ES2015 solution. Keeps existing values.
const set = (obj, path, val) => {
const keys = path.split('.');
const lastKey = keys.pop();
const lastObj = keys.reduce((obj, key) =>
obj[key] = obj[key] || {},
obj);
lastObj[lastKey] = val;
};
Example:
const obj = {'a': {'prop': {'that': 'exists'}}};
set(obj, 'a.very.deep.prop', 'value');
console.log(JSON.stringify(obj));
// {"a":{"prop":{"that":"exists"},"very":{"deep":{"prop":"value"}}}}

Using ES6 is shorten. Set your path into an array.
first, you have to reverse the array, to start filling the object.
let obj = ['a','b','c'] // {a:{b:{c:{}}}
obj.reverse();
const nestedObject = obj.reduce((prev, current) => (
{[current]:{...prev}}
), {});

Another recursive solution:
var nest = function(obj, keys, v) {
if (keys.length === 1) {
obj[keys[0]] = v;
} else {
var key = keys.shift();
obj[key] = nest(typeof obj[key] === 'undefined' ? {} : obj[key], keys, v);
}
return obj;
};
Example usage:
var dog = {bark: {sound: 'bark!'}};
nest(dog, ['bark', 'loudness'], 66);
nest(dog, ['woff', 'sound'], 'woff!');
console.log(dog); // {bark: {loudness: 66, sound: "bark!"}, woff: {sound: "woff!"}}

I love this ES6 immutable way to set certain value on nested field:
const setValueToField = (fields, value) => {
const reducer = (acc, item, index, arr) => ({ [item]: index + 1 < arr.length ? acc : value });
return fields.reduceRight(reducer, {});
};
And then use it with creating your target object.
const targetObject = setValueToField(['one', 'two', 'three'], 'nice');
console.log(targetObject); // Output: { one: { two: { three: 'nice' } } }

Lodash has a _.set method to achieve this
let obj = {}
_.set(obj, ['a', 'b', 'c', 'd'], 'e')
or
_.set(obj, 'a.b.c.d', 'e')
// which generate the following object
{
"a": {
"b": {
"c": {
"d": "e"
}
}
}
}

Here is a simple tweak to jlgrall's answer that allows setting distinct values on each element in the nested hierarchy:
var createNestedObject = function( base, names, values ) {
for( var i in names ) base = base[ names[i] ] = base[ names[i] ] || (values[i] || {});
};
Hope it helps.

Here is a functional solution to dynamically create nested objects.
const nest = (path, obj) => {
const reversedPath = path.split('.').reverse();
const iter = ([head, ...tail], obj) => {
if (!head) {
return obj;
}
const newObj = {[head]: {...obj}};
return iter(tail, newObj);
}
return iter(reversedPath, obj);
}
Example:
const data = {prop: 'someData'};
const path = 'a.deep.path';
const result = nest(path, data);
console.log(JSON.stringify(result));
// {"a":{"deep":{"path":{"prop":"someData"}}}}

Inspired by ImmutableJS setIn method which will never mutate the original. This works with mixed array and object nested values.
function setIn(obj = {}, [prop, ...rest], value) {
const newObj = Array.isArray(obj) ? [...obj] : {...obj};
newObj[prop] = rest.length ? setIn(obj[prop], rest, value) : value;
return newObj;
}
var obj = {
a: {
b: {
c: [
{d: 5}
]
}
}
};
const newObj = setIn(obj, ["a", "b", "c", 0, "x"], "new");
//obj === {a: {b: {c: [{d: 5}]}}}
//newObj === {a: {b: {c: [{d: 5, x: "new"}]}}}

Appreciate that this question is mega old! But after coming across a need to do something like this in node, I made a module and published it to npm.
Nestob
var nestob = require('nestob');
//Create a new nestable object - instead of the standard js object ({})
var newNested = new nestob.Nestable();
//Set nested object properties without having to create the objects first!
newNested.setNested('biscuits.oblong.marmaduke', 'cheese');
newNested.setNested(['orange', 'tartan', 'pipedream'], { poppers: 'astray', numbers: [123,456,789]});
console.log(newNested, newNested.orange.tartan.pipedream);
//{ biscuits: { oblong: { marmaduke: 'cheese' } },
orange: { tartan: { pipedream: [Object] } } } { poppers: 'astray', numbers: [ 123, 456, 789 ] }
//Get nested object properties without having to worry about whether the objects exist
//Pass in a default value to be returned if desired
console.log(newNested.getNested('generic.yoghurt.asguard', 'autodrome'));
//autodrome
//You can also pass in an array containing the object keys
console.log(newNested.getNested(['chosp', 'umbridge', 'dollar'], 'symbols'));
//symbols
//You can also use nestob to modify objects not created using nestob
var normalObj = {};
nestob.setNested(normalObj, 'running.out.of', 'words');
console.log(normalObj);
//{ running: { out: { of: 'words' } } }
console.log(nestob.getNested(normalObj, 'random.things', 'indigo'));
//indigo
console.log(nestob.getNested(normalObj, 'improbable.apricots'));
//false

Inside your loop you can use lodash.set and will create the path for you:
...
const set = require('lodash.set');
const p = {};
const [type, lang, name] = f.split('.');
set(p, [lang, type, name], '');
console.log(p);
// { lang: { 'type': { 'name': '' }}}

try using recursive function:
function createSetting(setting, value, index) {
if (typeof index !== 'number') {
index = 0;
}
if (index+1 == setting.length ) {
settings[setting[index]] = value;
}
else {
settings[setting[index]] = {};
createSetting(setting, value, ++index);
}
}

I think, this is shorter:
Settings = {};
newSettingName = "Modules_Floorplan_Image_Src";
newSettingValue = "JWPlayer";
newSettingNameArray = newSettingName.split("_");
a = Settings;
for (var i = 0 in newSettingNameArray) {
var x = newSettingNameArray[i];
a[x] = i == newSettingNameArray.length-1 ? newSettingValue : {};
a = a[x];
}

I found #jlgrall's answer was great but after simplifying it, it didn't work in Chrome. Here's my fixed should anyone want a lite version:
var callback = 'fn.item1.item2.callbackfunction',
cb = callback.split('.'),
baseObj = window;
function createNestedObject(base, items){
$.each(items, function(i, v){
base = base[v] = (base[v] || {});
});
}
callbackFunction = createNestedObject(baseObj, cb);
console.log(callbackFunction);
I hope this is useful and relevant. Sorry, I've just smashed this example out...

You can define your own Object methods; also I'm using underscore for brevity:
var _ = require('underscore');
// a fast get method for object, by specifying an address with depth
Object.prototype.pick = function(addr) {
if (!_.isArray(addr)) return this[addr]; // if isn't array, just get normally
var tmpo = this;
while (i = addr.shift())
tmpo = tmpo[i];
return tmpo;
};
// a fast set method for object, put value at obj[addr]
Object.prototype.put = function(addr, val) {
if (!_.isArray(addr)) this[addr] = val; // if isn't array, just set normally
this.pick(_.initial(addr))[_.last(addr)] = val;
};
Sample usage:
var obj = {
'foo': {
'bar': 0 }}
obj.pick('foo'); // returns { bar: 0 }
obj.pick(['foo','bar']); // returns 0
obj.put(['foo', 'bar'], -1) // obj becomes {'foo': {'bar': -1}}

A snippet for those who need to create a nested objects with support of array keys to set a value to the end of path. Path is the string like: modal.product.action.review.2.write.survey.data. Based on jlgrall version.
var updateStateQuery = function(state, path, value) {
var names = path.split('.');
for (var i = 0, len = names.length; i < len; i++) {
if (i == (len - 1)) {
state = state[names[i]] = state[names[i]] || value;
}
else if (parseInt(names[i+1]) >= 0) {
state = state[names[i]] = state[names[i]] || [];
}
else {
state = state[names[i]] = state[names[i]] || {};
}
}
};

Set Nested Data:
function setNestedData(root, path, value) {
var paths = path.split('.');
var last_index = paths.length - 1;
paths.forEach(function(key, index) {
if (!(key in root)) root[key] = {};
if (index==last_index) root[key] = value;
root = root[key];
});
return root;
}
var obj = {'existing': 'value'};
setNestedData(obj, 'animal.fish.pet', 'derp');
setNestedData(obj, 'animal.cat.pet', 'musubi');
console.log(JSON.stringify(obj));
// {"existing":"value","animal":{"fish":{"pet":"derp"},"cat":{"pet":"musubi"}}}
Get Nested Data:
function getNestedData(obj, path) {
var index = function(obj, i) { return obj && obj[i]; };
return path.split('.').reduce(index, obj);
}
getNestedData(obj, 'animal.cat.pet')
// "musubi"
getNestedData(obj, 'animal.dog.pet')
// undefined

Try this: https://github.com/silkyland/object-to-formdata
var obj2fd = require('obj2fd/es5').default
var fd = obj2fd({
a:1,
b:[
{c: 3},
{d: 4}
]
})
Result :
fd = [
a => 1,
b => [
c => 3,
d => 4
]
]

Here is a decomposition to several useful functions, that each preserve existing data. Does not handle arrays.
setDeep: Answers question. Non-destructive to other data in the object.
setDefaultDeep: Same, but only sets if not already set.
setDefault: Sets a key if not already set. Same as Python's setdefault.
setStructure: Helper function that builds the path.
// Create a nested structure of objects along path within obj. Only overwrites the final value.
let setDeep = (obj, path, value) =>
setStructure(obj, path.slice(0, -1))[path[path.length - 1]] = value
// Create a nested structure of objects along path within obj. Does not overwrite any value.
let setDefaultDeep = (obj, path, value) =>
setDefault(setStructure(obj, path.slice(0, -1)), path[path.length - 1], value)
// Set obj[key] to value if key is not in object, and return obj[key]
let setDefault = (obj, key, value) =>
obj[key] = key in obj ? obj[key] : value;
// Create a nested structure of objects along path within obj. Does not overwrite any value.
let setStructure = (obj, path) =>
path.reduce((obj, segment) => setDefault(obj, segment, {}), obj);
// EXAMPLES
let temp = {};
// returns the set value, similar to assignment
console.log('temp.a.b.c.d:',
setDeep(temp, ['a', 'b', 'c', 'd'], 'one'))
// not destructive to 'one'
setDeep(temp, ['a', 'b', 'z'], 'two')
// does not overwrite, returns previously set value
console.log('temp.a.b.z: ',
setDefaultDeep(temp, ['a', 'b', 'z'], 'unused'))
// creates new, returns current value
console.log('temp["a.1"]: ',
setDefault(temp, 'a.1', 'three'))
// can also be used as a getter
console.log("temp.x.y.z: ",
setStructure(temp, ['x', 'y', 'z']))
console.log("final object:", temp)
I'm not sure why anyone would want string paths:
They are ambiguous for keys with periods
You have to build the strings in the first place

Since I started with something from this page, I wanted to contribute back
Other examples overwrote the final node even if it was set, and that wasn't what I wanted.
Also, if returnObj is set to true, it returns the base object. By default, falsy, it returns the deepest node.
function param(obj, path, value, returnObj) {
if (typeof path == 'string') path = path.split(".");
var child = obj;
path.forEach((key, i) => {
if (!(key in child)) {
child[key] = (i < path.length-1) ? {} : value || {};
}
child = child[key];
});
return returnObj ? obj : child;
}
var x = {};
var xOut = param(x, "y.z", "setting")
console.log(xOut);
xOut = param(x, "y.z", "overwrite") // won't set
console.log(xOut);
xOut = param(x, "y.a", "setting2")
console.log(xOut);
xOut = param(x, "y.a", "setting2", true) // get object rather than deepest node.
console.log(xOut);
You can also do something where numeric keys are placed in arrays (if they don't already exist). Note that numeric keys won't convert to arrays for the first element of the path, since that's set by the type of your base-object.
function isNumber(n) {
return !isNaN(parseFloat(n)) && isFinite(n);
}
function param(obj, path, value, returnObj) {
if (typeof path == 'string') path = path.split(".");
var child = obj;
path.forEach((key, i) => {
var nextKey = path[i+1];
if (!(key in child)) {
child[key] = (nextKey == undefined && value != undefined
? value
: isNumber(nextKey)
? []
: {});
}
child = child[key];
});
return returnObj ? obj : child;
}
var x = {};
var xOut = param(x, "y.z", "setting")
console.log(xOut);
xOut = param(x, "y.z", "overwrite") // won't set
console.log(xOut);
xOut = param(x, "y.a", "setting2")
console.log(xOut);
xOut = param(x, "y.a", "setting2", true) // get object rather than deepest node.
xOut = param(x, "1.0.2.a", "setting")
xOut = param(x, "1.0.1.a", "try to override") // won't set
xOut = param(x, "1.0.5.a", "new-setting", true) // get object rather than deepest node.
console.log(xOut);
Naturally, when the numeric keys are greater than 0, you might see some undefined gaps.
Practical uses of this might be
function AddNote(book, page, line) {
// assume a global global notes collection
var myNotes = param(allNotes, [book, page, line], []);
myNotes.push('This was a great twist!')
return myNotes;
}
var allNotes = {}
var youthfulHopes = AddNote('A Game of Thrones', 4, 2, "I'm already hooked, at least I won't have to wait long for the books to come out!");
console.log(allNotes)
// {"A Game of Thrones": [undefined, undefined, undefined, undefined, [undefined, undefined, ["I'm already hooked, at least I won't have to wait long for the books to come out!"]]]}
console.log(youthfulHopes)
// ["I'm already hooked, at least I won't have to wait long for the books to come out!"]

function initPath(obj, path) {
path.split('.').reduce((o, key) => (
Object.assign(o, {[key]: Object(o[key])}),
o[key]
), obj);
return obj;
}
Usage
const obj = { a: { b: 'value1' } };
initPath(obj, 'a.c.d').a.c.d='value2';
/*
{
"a": {
"b": "value1",
"c": {
"d": "value2"
}
}
}
*/

simple answer. on es6, im using this
const assign = (obj, path, value) => {
let keyPath = path.split('.')
let lastKeyIndex = keyPath.length - 1
for (let i = 0; i < lastKeyIndex; ++i) {
let key = keyPath[i]
if (!(key in obj)) {
obj[key] = {}
}
obj = obj[key]
}
obj[keyPath[lastKeyIndex]] = value
}
example json
const obj = {
b: 'hello'
}
you can add new key
assign(obj, 'c.d.e', 'this value')
and you get like bellow
console.log(obj)
//response example
obj = {
b: 'hello',
c: {
d: {
e: 'this value'
}
}
}

function createObj(keys, value) {
let obj = {}
let schema = obj
keys = keys.split('.')
for (let i = 0; i < keys.length - 1; i++) {
schema[keys[i]] = {}
schema = schema[keys[i]]
}
schema[keys.pop()] = value
return obj
}
let keys = 'value1.value2.value3'
let value = 'Hello'
let obj = createObj(keys, value)

Eval is probably overkill but the result is simple to visualize, with no nested loops or recursion.
function buildDir(obj, path){
var paths = path.split('_');
var final = paths.pop();
for (let i = 1; i <= paths.length; i++) {
var key = "obj['" + paths.slice(0, i).join("']['") + "']"
console.log(key)
eval(`${key} = {}`)
}
eval(`${key} = '${final}'`)
return obj
}
var newSettingName = "Modules_Video_Plugin_JWPlayer";
var Settings = buildDir( {}, newSettingName );
Basically you are progressively writing a string "obj['one']= {}", "obj['one']['two']"= {} and evaling it;

typescript : logic to covert string array into custom object

Here is my requirement. I was able to achieve to some level in java but we need to move it to typescript (client side).
Note: The below input is for example purpose and may vary dynamically.
Input
var input = ["a.name", "a.type", "b.city.name" , "b.city.zip", "b.desc","c"];
We need to create an utility function that takes above input and returns output as below.
Output:
Should be string not an object or anything else.
"{ a { name, type }, b { city {name, zip } , desc }, c }"
any help is much appreciated.

I don't see that typescript plays any role in your question, but here's a solution for constructing the string you requested. I first turn the array into an object with those properties, then have a function which can turn an object into a string formatted like you have
const input = ["a.name", "a.type", "b.city.name" , "b.city.zip", "b.desc","c"];
const arrayToObject = (arr) => {
return arr.reduce((result, val) => {
const path = val.split('.');
let obj = result;
path.forEach(key => {
obj[key] = obj[key] || {};
obj = obj[key];
});
return result;
}, {});
}
const objectToString = (obj, name = '') => {
const keys = Object.keys(obj);
if (keys.length === 0) {
return name;
}
return `${name} { ${keys.map(k => objectToString(obj[k], k)).join(', ')} }`;
}
const arrayToString = arr => objectToString(arrayToObject(arr));
console.log(arrayToString(input));

Here's another variation. Trick is to parse the strings recursively and store the intermediate results in an Object.
function dotStringToObject(remainder, parent) {
if (remainder.indexOf('.') === -1) {
return parent[remainder] = true
} else {
var subs = remainder.split('.');
dotStringToObject(subs.slice(1).join('.'), (parent[subs[0]] || (parent[subs[0]] = {})))
}
}
var output = {};
["a.name", "a.type", "b.city.name" , "b.city.zip", "b.desc","c"].forEach(function(entry) {
dotStringToObject(entry, output)
});
var res = JSON.stringify(output).replace(/\"/gi, ' ').replace(/\:|true/gi, '').replace(/\s,\s/gi, ', ');
console.log(res)
// Prints: { a { name, type }, b { city { name, zip }, desc }, c }

You could do something like this:
var input = ["a.name", "a.type", "b.city.name" , "b.city.zip", "b.desc","c"];
var output = {};
for(var i =0; i < input.length; i+=2){
output[String.fromCharCode(i+97)] = {};
output[String.fromCharCode(i+97)].name = input[i];
output[String.fromCharCode(i+97)].type = input[i+1];
}
console.log(JSON.stringify(output));

filter unique properties from array of objects with unique values if existing then override the value

I am trying to iterate array of objects with different properties. where I am adding objects dynamically and want to check whether the property of the object is exist in the array then only override the value else add it to the array.
For e.x.
var arr = [
{"value":"abc"},
{"type":"def"},
{"status":"ghi"},
{"value":"xyz"}
]
expected result:
arr = [
{"value":"xyz"},
{"type":"def"},
{"status":"ghi"}
]
What I am trying so far is not working. Here is my code:
var arr = [
{"value":"abc"},
{"type":"def"},
{"status":"ghi"},
{"value":"abc"}
]
var obj={};
var key1 = "type", value="xyz";
obj[key1] = value;
var newarr = arr.filter(function(entry,i) {
if (!entry.hasOwnProperty(key1)) {
return true;
}
});
newarr.push(obj);
Please note, the obj will be dynamic so my code is working fine for first time when the property of key1 doesn't change. once I change the value of key1 from "type" to "status", It is adding objects 2 times.
Can anybody help me around this?

Try this Array.reduce() function and Object.keys() method.
array#reduce() used to recreate with new array
Object.keys() get the key of the each object .Array#map() create the array of all object keys .
Then match if not includes in the array then push with new array
Updated replace the type with new one value
var arr = [{"value":"abc"}, {"type":"def"}, {"status":"ghi"}, {"value":"xyz"}];
var key1 = "type";
var value="xyz";
var result = arr.reduce((a,b) =>{
if(!a.map(i=> Object.keys(i)[0]).includes(Object.keys(b)[0]))
{
if(b.hasOwnProperty(key1)){
b[key1]=value
}
a.push(b)
}
return a}, []);
console.log(result);

The following code should do the job:
var arr = [
{"value":"abc"},
{"type":"def"},
{"status":"ghi"},
{"value":"xyz"}
];
var obj = {};
for (i in arr) {
key = Object.keys(arr[i])[0];
obj[key] = arr[i][key];
}
console.log(obj);

The solution using ES6 Array.prototype.reduce() and Object.assign() functions:
var arr = [{"value":"abc"}, {"type":"def"}, {"status":"ghi"}, {"value":"xyz"}],
obj = arr.reduce((r,o) => Object.assign(r,o), {}),
result = Object.keys(obj).map( (k) => { o = {}; o[k]=obj[k]; return o } );
console.log(result);

You could use a hash table and filter and update all found same key objects.
var array = [{ value: "abc" }, { type: "def" }, { status: "ghi" }, { value: "ddd" }],
key = "type",
value = "xyz",
update = false,
hash = Object.create(null),
temp = {};
temp[key] = value;
array.push(temp);
array = array.filter(function (o) {
var key = Object.keys(o)[0];
if (!hash[key]) {
hash[key] = o;
return true;
}
hash[key][key] = o[key];
});
console.log(array);
.as-console-wrapper { max-height: 100% !important; top: 0; }

reduce key value pairs in JS Array to object

I have one object that I had to take apart into two arrays to handle properly.
It looked like this:
{
city:"stuttgart",
street:"randomstreet",
...
}
Since it needs to fit a certain directive I had to convert it to:
[
{key:"city", value:"stuttgart"}
{key:"street", value:"randomstreet"},
...
]
for this I first used
var mapFromObjectWithIndex = function (array) {
return $.map(array, function(value, index) {
return [value];
});
};
var mapFromObjectWithValue = function (array) {
return $.map(array, function(value, index) {
return [index];
});
});
to create two arrays, one containing the old key, the other one is holding the old value. Then I created another, two dimensional array map them into a single array doing this
var mapToArray = function (arrayValue, arrayIndex) {
var tableData = [];
for (var i = 0; i<arrayIndex.length; i++){
tableData[i] = {key:arrayIndex[i] , value:arrayValue[i]};
}
return tableData;
};
(maybe I have already messed up by here, can this be done any easier?)
Now, I use the array (tableData) to display the data in a form. The value fields can be edited. In the end, I want to convert the array (tableData) to its original. (see first object)
Please note, that the original object doesn't only contain strings as values, but can also contain objects as well.

I think conversion can be definitely easier:
var obj = {
city:"stuttgart",
street:"randomstreet",
};
var tableData = Object.keys(obj).map(k => {return {key: k, value: obj[k]}});
console.log(tableData);
var dataBack = {};
tableData.forEach(o => dataBack[o.key] = o.value);
console.log(dataBack);
What do you want to do with objects? Do you want to expand them as well? If yes you can do something like this (and it works with nested objects as well):
var obj = {
city:"stuttgart",
street:"randomstreet",
obj: {a: 'a', b: 'b'},
subObject: {aha: {z: 'z', y: 'y'}}
};
function trasformToTableData(obj) {
if (typeof obj !== 'object') return obj;
return Object.keys(obj).map(k => {return {key: k, value: trasformToTableData(obj[k])}});
}
var tableData = trasformToTableData(obj);
console.log(tableData);
function transformBack(obj) {
if (Array.isArray(obj)) {
var support ={};
for (let i = 0; i < obj.length; i++) {
support[obj[i].key] = transformBack(obj[i].value)
}
return support;
}
return obj;
}
var dataBack = {};
tableData.forEach(o => dataBack[o.key] = transformBack(o.value));
console.log(dataBack);

Let's have some fun and turn our object into iterable to do the job as follows;
var input = {city:"stuttgart", street:"randomstreet", number: "42"};
output = [];
input[Symbol.iterator] = function*(){
var ok = Object.keys(this),
i = 0;
while (i < ok.length) yield {key : ok[i], value: this[ok[i++]]};
};
output = [...input];
console.log(output);

This function will map your object to an array when you call objVar.mapToArray(), by using Object.keys() and .map()
Object.prototype.mapToArray = function() {
return Object.keys(this).map(function(v) {
return { key: v, value: this[v] };
}.bind(this));
}

I would do something like this:
var dataObj = {
city:"stuttgart",
street:"randomstreet",
};
function toKeyValue(obj) {
var arr = [];
for (var key in obj) {
if(obj.hasOwnProperty(key)) {
arr.push({'key': key, 'value': obj[key]});
}
}
return arr;
}
var arrayKeyValue = toKeyValue(dataObj);
console.log(arrayKeyValue);

Merge hash with properties arrays

I have 2 hashes(objects) for ex.
hash1 = {myKey: ["string1"]}
hash2 = {myKey: ["string2"]}
I want to merge them together, so in the end i would get something like following -
{myKey: ["string1", "string2"] }
I tried $.extend, but that doesnt work for arrays as property

You can take a function for that.
function add(o, v) {
Object.keys(v).forEach(function (k) {
o[k] = o[k] || [];
v[k].forEach(function (a) {
o[k].push(a);
});
});
}
var hash1 = { myKey: ["string1"] },
hash2 = { myKey: ["string2"] };
add(hash1, hash2);
document.write('<pre>' + JSON.stringify(hash1, 0, 4) + '</pre>');

Note: check the case sensitivity of your keys.
You can do something like this:
hash1 = {myKey: ["string1"]}
hash2 = {myKey: ["string2"]}
var result = {};
for (var hash1Key in hash1) {
if (hash1.hasOwnProperty(hash1Key)) {
for (var hash2Key in hash2) {
if (hash2.hasOwnProperty(hash2Key)) {
if (hash1Key === hash2Key) {
result[hash1Key] = [hash1[hash1Key], hash2[hash2Key]]
}
}
}
}
}
See it live in jsFiddle

You can Array.prototype.push.apply() to merge array
var hash1 = {myKey: ["string1"]};
var hash2 = {myKey: ["string1"]};
Array.prototype.push.apply(hash1.myKey, hash2.myKey)
console.log(hash1)